This is a two-card combo, comprised of Tainted Pact and Jace, Wielder of Mysteries. The deck is built so no other card has more than just one copy. This way, with the Pact and Jace in hand, we can win as early as turn-4, by casting the Pact during the opponent's turn, exiling most of our library, and using Jace's +1 ability on our turn.

"You already lost. You just don't know it yet."

Of course, having just one copy of each other card makes the deck less reliable. That's why we need to prioritize flexible cards, such as Drown in the Loch and Thassa's Intervention, in the main deck. The fun part is actually building the rest of the deck outside of the combo, adding cards with each new set and making the deck our own. I would say going for a controlling approach is optimal, since we need to survive until we can combo-off, as well as protect our combo pieces. That's why this list contains a mix of removal, card selection, discard and counterspells, as well as tutors, such as Dig Up and Wishclaw Talisman, to fetch specific tools and the combo pieces. Other than being half of the combo, Jace is also a pretty great source of card advantage.

The cool thing about Tainted Pact in this deck is that it can either get rid of the whole library for Jace, or act as a sort-of tutor. When casting the Pact, if we don't have Jace in hand, it is best to stop either when we find the card we are looking for or when we find the first Jace. Otherwise, we might exile both Jaces and end up with just manlands as our win-condition.

Lastly, we have to be careful not to lose Jace to removal before using his +1 ability to win the game. In this case, we can try finding a counterspell or discard spell before going for the combo, or even a cycler to keep in hand, so we can draw in response. We need to be mindful of an opposing Narset, Parter of Veils though.

Against aggro, we act simply as a control deck, but the catch is that we can end the game quickly if we find the combo. Control is a tricky match-up, but much more favourable post-board, as we add some instant speed spells, such as Siphon Insight, and the silver bullet: Thought Distortion.